The effect of changing climate on the frequency of absolute extreme events

Editor’s Note: Occasionally papers are published in less limited distribution journals that deserve to be more widely read. The following paper by Tom Wigley is one of these – it presents some simple analyses of extreme event theory that lie on the boundary between textbook and scientific journal material and so tend to slip between the cracks. Since the original publication of this paper, interest in and understanding of extreme events has developed rapidly. To provide a bridge to the present state of the art, an updated review of the subject is given in the accompanying paper by Dan Cooley.

Author’s Note: I wrote this paper more than 20 years ago for publication in the Climatic Research Unit’s in-house journal “Climate Monitor”. This was at a time when the interest in possible anthropogenic changes in the frequency of extreme events was just beginning, and the paper was presented primarily as a pedagogical piece to explain certain relatively simple aspects of extreme-event theory such as risk and return period. In addition, I made some predictions of the likelihood of future extremes that have been borne out by, for example, the record-breaking hot summer of 2003 in Europe. These simple results have not appeared in the literature subsequently. The original paper was not refereed, but this reprint was refereed for publication in Climatic Change.